The present invention relates to a droplet ejection apparatus, a method for forming a functional film, an apparatus for forming a liquid crystal alignment film, a method for forming a liquid crystal alignment film of a liquid crystal display, and a liquid crystal display that are capable of efficiently forming a uniform functional film such as a liquid crystal alignment film on a substrate.
As a method for forming a functional film such as a liquid crystal alignment film of a liquid crystal display, a method using a droplet ejection apparatus is known. By this method, a functional film with a desired thickness is accurately formed at a desired position. The method is thus advantageous particularly as a method for forming a liquid crystal alignment film.
To form a liquid crystal alignment film, a plurality of coating dots are provided on a substrate by ejecting droplets of liquid composition for forming a liquid crystal alignment film on the substrate through a droplet ejection apparatus. The coating dots are then dried to form the liquid crystal alignment film. Typically, the composition for forming the liquid crystal alignment film is highly volatile. This may vary the time spent for drying the coating dots, causing unevenness on the liquid crystal alignment film, such as lines or drying marks. This makes it impossible to provide a uniform liquid crystal alignment film.
To solve this problem, an apparatus for forming an alignment film of JP-A-2005-221890 includes a plurality of nozzles that are spaced at intervals of 60 μm to 120 μm. Droplets are thus ejected onto a substrate in such a manner that each coating dot partly overlaps with adjacent coating dots.
However, a liquid crystal alignment film formed by the apparatus of JP-A-2005-221890 includes a relatively large area of overlapped portions between adjacent pairs of the coating dots. This increases the consumption amount of a composition for forming the liquid crystal alignment film, which raises the cost, and makes it difficult to form a film with extremely small thickness. Further, to form the overlapped portions between the adjacent pairs of the coating dots, the pitch between each adjacent pair of the nozzles is set to a relatively small value. This may vary the ejection amount among the nozzles due to mutual influence (cross-talking) between the adjacent nozzles, hampering formation of a uniform film. Also, the droplets may splash and clog some of the nozzles after having been ejected from the adjacent ones of the nozzles.